A pulse generator is used to emit a pulse train of specific frequency while two pick-ups--one adjacent a circumferential array of control lugs on the rotor and the other adjacent the blades--emit start counting and stop counting pulses. The number of pulses generated by an external pulse generator are counted during the time interval for the passage of two lugs past a pick-up and the time interval for the passage of two adjacent blades past a pick-up for each revolution of the rotor. A quotient is then obtained from the two pulse numbers for each revolution and the difference between the maximum and minimum values of the quotients obtained during continued rotation is determined. If the difference exceeds a preset critical value, an activity signal is generated, for example to set off an alarm.
A system for use in a gas-turbine engine, for controlling the clearance between the tips of the blades and a surrounding shroud, has a probe mounted in the shroud. A microwave oscillator supplies microwave energy to the probe which propagates energy towards the blades and receives energy reflected from the blades. A mixer is mounted remote from the probe and mixes the energy reflected from the blades with a reference signal derived either from energy transmitted by the oscillator or from the energy reflected by the tip of the probe. This produces interference dependent upon the phase difference between the energy reflected by the blades and the reference signal. From this phase difference, the system derives an indication of the separation of the blades from the probe and uses this to displace the shroud along its length, thereby altering the clearance between the tips of the blades and the shroud.
A multiple parameter sensor is disclosed having a preferred application in a turbine used in an auxiliary power unit. The multiple parameter sensor includes a first part (12) for rotation with a rotating member (14) having a speed of rotation to be measured; a second part (20) mounted in a fixed position adjacent the first part to respond to the speed of rotation of the first part to produce a first periodic signal (22), the second part in response to the first periodic signal producing a second signal representing the speed of rotation of the rotating member and comprising electrical winding (26) in which the first periodic signal is magnetically induced by rotation of the first part with the rotating member; and wherein the second part produces at least one additional signal with each additional signal representing one additional parameter of operation of the device associated with the rotating member.
A speed and phase sensor counterrotates aircraft propellers. A toothed wheel is attached to each propeller, and the teeth trigger a sensor as they pass, producing a sequence of signals. From the sequence of signals, rotational speed of each propeller is computer based on time intervals between successive signals. The speed can be computed several times during one revolution, thus giving speed information which is highly up-to-date. Given that spacing between teeth may not be uniform, the signals produced may be nonuniform in time. Error coefficients are derived to correct for nonuniformities in the resulting signals, thus allowing accurate speed to be computed despite the spacing nonuniformities. Phase can be viewed as the relative rotational position of one propeller with respect to the other, but measured at a fixed time. Phase is computed from the signals.
A system combining a transducer and a signal processing circuit measures the clearance distance from the transducer to an electrically conductive moving part of a machine. The transducer contains a magnet and a coil, both coupled magnetically to a region traversed by the machine part. Eddy currents are induced in the part as it passes through the magnetic field of the transducer. These currents produce a field which moves with the part and generates a characteristic signal in the transducer coil. Amplitude and timing attributes of the signal are measured by the signal processing circuit. An experimentally derived mathematical function which relates the amplitude and timing of this signal to the clearance distance between the transducer and the moving part is used to compute the clearance distance. During this calculation useful information is also developed about the speed and transit time of the moving part. The system is adapted to turbomachinery blade condition monitoring.
A nonsynchronous turbine blade vibration monitoring system is comprised of a maximum of two sensors circumferentially mounted along the turbine blade row for detecting the actual arrival times of the turbine blades at the sensors. Expected arrival times of the turbine blades at the sensors are determined and then compared to the actual arrival times in order to obtain turbine blade deflection data. Harmonic analysis is then performed on the blade deflection data to determine the level of vibration at each non-integral harmonic.
